Modification Of Biodegradable Poly(propylene Carbonate)

This paper introduced the physics modification of poly(propylenecarbonate)(PPC) using solution blends methods. The mechanicalproperties and micro-morphology of PPC/Lignin fiber were investigatedwith SMTA and SEM. The compatibility, thermal properties, mechanicalproperties, phase structure and morphology of PPC/PLLA wereinvestigated with TG,DSC,SEM,POM,WAXD and AFM in detail inthis work. By analyzing the relationship between their structure andperformance, The performance of PPC can be improved and itapplications field can be provided on a basis.(1)The PPC/Lignin fiber blends were prepared via solution castingmethod in this work. Mechanical testing showed that, joining the ligninfiber can be effective in improving the mechanical strength of the PPC,but its tenacity has a certain amount of damage. When control the ligninfiber at15WT%, the blends can have a good strength and not badtoughness. The dispersion and morphology of lignin fiber in the PPCmatrix was studied by scanning electron microscopy (SEM). Dispersionresearch suggests that the compatibility between lignin fiber and PPC is not very good but there is a certain degree of compatibility. This can alsoexplained why PPC can be modified by blending with lignin fiber to acertain extent.(2)The PPC/PLLAblends were prepared via solution casting method inthis work. TG DSC and SEM results suggested that PLLA and PPC arepartially miscible but are compatible to some extent. TG chart can alsoindicate that the addition of PLLA can significantly improve the stabilityof PPC. In addition, SEM results suggested that PPC and PLLA blendscould form a typical "Sea-Island" structure, When PLLA content is lessthan50%, the PPC acted as continuous phase and PLLA dispersed in it,When the content of PLLA is greater than50%, System occurred phasereversal, PLLA act as continuous phase while PPC is dispersedphase.Mechanical test results showed that PLLA played a role inenhancing PPC, at the same time PPC also has a very significant role intoughening PLLA, which also indicate PLLA and PPC are partiallymiscible. The phase structure of PPC/PLLA blends with differentcontents or different processing conditions were investigated with POMin detail in this work. The different PPC/PLLA proportions affectedclearly on their phase structure under the same crystallization conditions,and the phase reversal occurred significantly when the contnet of PPC is40wt%. The phase separations started in the molten process. ForPPC/PLLA blends with the same mixing ratio40/60, PLLA gradually changed from dispersed phase into the continuous phase with increasingthe melting temperature or melting time. In addition, their size of thephase domain increased gradually with elevating the crystallizationtemperature. The crystallization behaviours of the PPC/PLLA40/60blends with different melting temperatures and melting time wereinvestigated by DSC. The crystallinity of the PLLA increased with theincrease of the melting temperature and melting time. And the meltingpoint Tm of PLLA became lower with the increased the meltingtemperature or the melting time. Mechanical testing also showed thatdifferent phase structures of composite materials' mechanical propertiesare different. WAXD results showed PPC/PLLA40/60blends and purePLLA had the same peak, This proved that PPC did not affect the crystalform of PLLA, which was still Alpha crystal. AFM results showed thePLLA in PPC/PLLA was flat-on crystal structure as the same as purePLLA.